Importance of Soil Amendments: Survival of Bacterial Pathogens in Manure and Compost Used as Organic Fertilizers

What is it about?

Biological soil amendments (BSA’s) like manure and compost can be nutrient-rich fertilizers for the cultivation of fruit and vegetable crops. However, animal manures are known to harbor enteric pathogens which can be transferred to fruits and vegetables, potentially leading to cases of foodborne illness through the consumption of contaminated produce. Under certain conditions pathogens have been shown to regrow and resuscitate in both manure-amended soils and compost. Other studies have indicated that manure application may lead to the introduction of bacteria harboring antibiotic-resistant genes to soils. The physicochemical characteristics (moisture content, type of soils, type of animal manure used) of the manure and soil affects the survival and potential regrowth of these pathogens in BSA’s. In some cases bacterial pathogens, may adapt to conditions in manure or compost-amended soils, extending their potential survival in these environments. In the United States there are several commodity-specific, current and proposed federal rules which provide guidance on the application of BSA’s as fertilizers to soils. Several of these guidelines and rules require an interval between the application of manure to soils and harvest to minimize the transfer of pathogens to fruits and vegetables. Overall, biological soil amendments applied as fertilizers to soils can support the survival and regrowth of pathogens. BSA’s should be handled and applied in a manner which reduces the prevalence of pathogens in soils and likelihood of transfer of foodborne pathogens to fruits and vegetables.

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Why is it important?

As sustainability becomes a topic that permeates through agricultural production, we need to address the intersection of food safety and sustainability. THe use of biological soil amendments provides a natural 'recycling' of animal wastes that can be used to grow fruits and vegetables, but appropriate risks of pathogen contamination need to be understood so that mitigation of these risks can occur.